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Hollinger Corp. 
P H 8.5 




Concrete for Permanence 



TV 

PROTECTING CONCRETE WORK 



Protecting Concrete Work Done 
In Warm Weather 

CONCRETE MUST NOT BE 
ALLOWED TO DRY OUT 

UNLESS concrete work is properly protected from rapid 
drying out for a few days after placing, its strength and 
wearing qualities will be considerably reduced. 

The hardening of concrete is not a drying process. In 
reality, concrete hardens best and most uniformly in the 




Protection given to concrete pavement by ponding, that is, flooding with water. 

The additional longitudinal dike at the side helps to prevent 

excessive loss of water by seepage. 

presence of moisture. Water is necessary to complete the 
chemical changes that take place when the cement and water 
are combined. Mixtures may have been properly propor- 
tioned, the concrete mixed to the right consistency and prop- 
erly placed, yet if the work is exposed to hot sun and drying 
winds its strength and hardness will fall below maximum. 

The protection which is necessary to the success of concrete 
work in cold weather is quite generally known, but many per- 
sons neglect to apply the necessary protection during the usual 
concreting season when hot sun and dry wind prevail almost daily. 

QU\ J > 




DONE IN WARM WEATHER 




This illustration shows canvas-covered frames used to protect the newly-finished 
concrete, also sprinkling the concrete surface to keep it moist. 



COMMON METHODS OF PRO- 
TECTING CONCRETE 

Generally speaking, the protection that should be given to 
concrete work during hot, dry weather is about the same for 
all classes of concrete work. Ways and means of applying it 
may differ slightly, but all aim to prevent the concrete from 
drying out. 

Pavements in general, which properly includes floors, side- 
walks, driveways, etc., expose a relatively larger area to the 
atmosphere than does mass concrete. Thin wall sections have 
a still greater area exposed to the atmosphere, usually two 
sides instead of one. 

Floors, walks, street and highway pavements may be pro- 
tected by very simple means. In very hot weather it is best 
to stretch canvas on frames over concrete street and highway 
pavement immediately after the surface has been struck off 
and floated. Then when the concrete has hardened enough 
so it will not be marked or pitted by covering with earth or 
other water-retaining material, 2 inches of this should be 
evenly spread over the surface. This covering should be 
sprinkled often enough each day to keep it always moist. 



PROTECTING CONCRETE WORK 




As soon as the concrete can be covered with a protective layer of earth without 
danger of pitting or marking the surface, such a covering should be ap- 
plied. This should be sprinkled frequently enough to keep it 
moist. The earth may be removed in a week or ten 
days, depending somewhat on the weather 
conditions and the speed with which 
the concrete has hardened. 



Concrete streets and roads should not be opened to traffic 
until all possibility of injury has passed — from three to four 
weeks or more after the last concrete was placed, depending 
on the weather conditions during that time. 

Walls of such structures as concrete silos and water tanks 
should be protected either by frequent sprinkling or preferably 
by hanging canvas or burlap over them. The canvas or bur- 
lap covering as well as the concrete should be sprinkled often 
to prevent loss of water from the concrete by evaporation. 
Sometimes, especially when temperatures are not extremely 
high, sprinkling of the concrete alone, if done at sufficiently 
frequent intervals, gives the desired protection. Concrete 
pavements are sometimes protected by flooding or ponding. 
When sufficient water is available this method is certain to 
produce good results. 

Small concrete watering troughs, such as would be used in 
the ordinary barnyard lot, should be covered with wet hay or 
straw and the covering be kept wet for several days. 



DONE IN WARM WEATHER 



Mass work, such as foundation walls, almost all of which are 
below ground, heavy abutments and retaining walls do not 
need the same extreme measures of protection as does work 
of thinner or exposed section. Leaving forms in place and 
occasional sprinkling or wetting down of the work for several 
days will usually give the necessary protection. 

Concrete roofs and thin building walls require about the 
same measures of protection, as both outside and inside sur- 
faces are more or less exposed. Roof slabs should be covered 
with moist earth or sand, just as protection is given to pave- 
ments and floors. Sprinkle the covering frequently. Keep 
the concrete moist. 

Stucco work may be ruined unless protected during hot 
weather. Walls must be wet down and the sides of the build- 
ing exposed to sun and wind be covered with canvas to prevent 
sun and wind from drying out the fresh stucco. 

CARING FOR MATERIALS 

Protection of concrete work in warm weather sometimes 
involves special attention to the sand and pebbles or broken 
stone. Sand piles may have been so exposed to sun and wind 
as to have thoroughly dried out and become heated. This 




Another example of protecting concrete pavement by canvas-covered 
frame, also showing sprinkling of earth_covering. 



PROTECTING CONCRETE WORK 



condition should be watched and where a certain quantity of 
water was determined necessary for a batch of concrete when 
the sand contained considerable moisture, the quantity of 
water must be varied as the sand becomes dryer, so as to secure 
the same consistency of batches throughout. 

In very hot weather it is desirable to keep cement in the 
shade. 

Use as cool water as possible to obtain. 




Keeping concrete pipe moist by sprinkling. 



PROTECTION FOR CONCRETE 
PRODUCTS 

Protect concrete products, such as fence posts, block, brick, 
tile, sewer pipe and similar concrete work of thin section. It 
is particularly important that the concrete be kept moist for 
several days before directly exposing to summer temperature 
conditions. Forms should not be removed if they can just as 
well be left in place. 

Wet concrete block and brick thoroughly when laying up in 
the wall during hot weather. If this is not done they will 
draw an excessive amount of water from the mortar, thus mak- 
ing mortar joints porous and weak because of loss of water. 

Cement sacks are too valuable to use for protecting concrete 
work. They should be carefully taken care of as emptied so 



DONE IN WARM WEATHER 



that they can be returned to the dealer or manufacturer in 
serviceable condition for redemption. 

i 

CONCRETING IN COLD 
WEATHER 

Only a few years ago many contractors and other concrete 
workers thought it necessary to stop concrete work with the 
approach of cold weather. Today cold-weather concreting 
practice has become so standardized that in most localities 
concreting is carried on throughout the entire year. 




Protecting concrete pipe from drying out by covering with wet 

burlap or similar material. The covering should be 

sprinkled frequently so as to keep it moist. 



Protection of concrete work done in cold weather requires 
that means be used to duplicate summer temperature condi- 
tions in the concrete itself. This is done by heating all the 
materials, although there are occasions when only the mixing 
water need be heated. The idea is to have the concrete of a 
certain temperature when placed and then to protect it in the 
forms so that this added temperature will not be lost until the 
concrete has acquired a certain degree of hardness. 

For full instructions as to cold weather concrete work, write 
the Portland Cement Association, 111 West Washington 
Street, Chicago, for its booklet "Concreting in Cold Weather. 



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j-JBRARY OF CONGRESS 

020 187 558 4 



Protect Your Concrete 

The best materials and 
the best workman- 
ship may count 
for nothing if the concrete 
is not protected while 
hardening. 



mmmmmmmmm 



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Portland Cement Association 

General Offices 
111 West Washington Street, Chicago 

Offices at 

ATLANTA KANSAS CITY PITTSBURGH 

Hurt Building Rialto Building Farmers Bank Building 

DALLAS MILWAUKEE SALT LAKE CITY 
Southwestern Life Bldg. First Nat. Bank Bldg. Kearns Building 

DENVER NEW YORK SAN FRANCISCO 

Ideal Building 101 Park Avenue Bialto Building 

INDIANAPOLIS PARKERSBURG, W. VA. SEATTLE 

1 Merchants Bank Bldg. Union Trust Building Northern Bank & Trust Bldg. 



1 



LIBRARY OF CONGRESS 



020 187 558 4 • 



